I saw a neat pattern for a marble machine in one of my woodworking magazines. I ordered the 30 page plan.
I often put plans I buy into Sketchup. It is how I learn the design, and most plans have at least one mistake in them. Using the booklet, I started putting the design into Sketchup.
Although there is a ton of drawings in the booklet, the over-all concepts were about as clear as mud to me. There are two main parts to the design in my mind.........the upper marble storage chamber with its releasing mechanism..........and the bottom mechanism that links back up to release another marble. In the booklet, I see no concept drawing showing the linkage between the upper and lower mechanisms? On the video of the machine he made for his grand-daughter, the lady said he used string to connect the two mechanisms.
The plans call for 1/4" thick handles, but the photos and video show about 3/4" thick handles? I will probably beef it up to the 3/4" thick version.
Although on one of the pages of the booklet it calls out for 1/4" thick handles, the BOM at back does call out 3/4" thick handles. I updated Sketchup to show this.
There are no dimensions for any of these parts, and they are not listed in the BOM in the back of the booklet. I scanned in the patterns and imported to Sketchup.........and I used the 9/16" hole to scale the drawing in Sketchup. I think I have it dimensioned correct.
It wasn't easy, but I think I figured out these 2 sub-assemblies in sketchup......
You must have to push up with a dowel to raise the ramp which releases the marble over the 2 dowels into the divider.
There are no exact dimensions for most of these parts, you are supposed to make from a pattern in the booklet. From a normal engineering perspective, one would make the passages maybe 1-1/16 wide versus the 1 inch nominal size of the balls. Now I will modify the widths in these 2 sub-assemblies to make them 1-1/16" wide. I also need to add 2 support on the top of the divider sub-assembly.
My son found another youtube video, which helps to explain the linkage between the top and bottom. You can view it using this link.
One thing I noticed on this video, was that he made it so the top release mechanism and divider can be removed from the back. I like this option, and may incorporate it into my design.
I went to designing this section next. I almost missed the little angled pieces at the corners........I guess when the marbles are stacking in the chutes, it must help them start to move as the marbles are consumed by the game?
It was not clear to me how this worked until I got all the pieces drawn and assembled. There are some assembly views in the plans which helped some. I don't know how the marbles get to the bucket, or how they leave, but will figure that out later I guess. A short piece of the red 1/4" dowel or rod is shown........this goes clear to the top somehow and released the next marble.
There was one assembly drawing that helped to explain this, but here is my isometric 3D view of the top part........
I wish this illustration was in the 34 page manual, because in my opinion, this explains most of how this mechanism works!
I think this finishes the mechanisms that cause the marbles to start moving, and then keep moving until they are all consumed. I think the next part is figuring out both marble paths to the bottom.
I followed the directions carefully and started building the RH track from the bottom down. An illustration of where the marble drops down into the chute would have been helpful !
The corner where the ball fall downs into the curved piece............the plan view in the booklet made no sense to me.......so I made the connection as best I could per the drawings above. My method would probably work ok.
Then I went to one of the videos looking for something else, and found out I did not do the corner joint the same as the plan booklet. The booklet method leaves the standard corner joint alone, where in my method you had to cut the bottom out.
The direction manual says to put a step every increment, of 7 increments in the circle..............which to me means 360/7 = 51.429 degrees. I revised my Sketchup drawing to include this on the steps.
I like the way the one guy made his top segment removable to illustrate how the marbles are stored and then released.............but you still can't see the release mechanism. What if I have the front and 2 side pieces go clear to the top, then the bottom of the marble storage chamber and the 4 sides made of 3/16" luan come out as a unit. You then lift the 3/16 Luan box off, which removes the chutes, leaving the release mechanism. Might give this a try later.
The top outer boards would have 3/16" thickness removed, to allow for the luan sides of the box.
I am not a great 3D thinker, so I struggled trying to look at the 4 photos and trying to follow all the marble paths. Slowly but surely, I am getting there.
My flipper has a little interference at the bottom, which probably means I need to reposition some of the marble chutes.
I am going to color code the 2 different marble paths in my drawing so my brain better understands them :)
It took me about 3 days, or 24 hours to enter this design into Sketchup!
My design is not perfect, e.g. I did not angle all the ends of the tracks to be vertical.........otherwise it is pretty close to the 34 page manual design.
I have designed, built, and repaired a lot of existing steps and staircases...........and I have never seen one where the horizontal steps are not horizontal???? I would think the marbles would get hung up and not go by gravity down the stairs with this design. I check the photos and videos, and it is hard to tell, but most them look to me like the as-built steps are horizontal. I will see what I can do in Sketchup and come up with my version.
I drew in the stair treads, then tipped all of them 2.5 degrees, so I may have less steps than the original design, but my design is guaranteed to work ok :)
I want the top assembly to slip out as a box...........then you lift the box walls (3/16" luan) off the box.......which is the track assembly...........leaving the bottom trip mechanism and divider.
Rather than having 2 vertical pieces on the front, RH side and LH side, I extended all 3 to the top. I then "carved out" 3/16" from the 1/2" walls on all 4 sides for the box to set in.
The plans call for a bunch of different thicknesses of Baltic Birch plywood. I don't keep baltic birch in my inventory.........but I have a ton of 3/16" Luan Plywood.......so I will be building my marble maze from 3/16" thick Luan and pine planed to the needed thicknesses. I picked up 2 boards 1x8 pine 8 feet long, and 6 boards 1x4 by 8 feet pine at the lumberyard for $60. Lumber is double normal price during the Pandemic so this normally would have been about $30.
I cut the 4 main verticals that make the core box. I do not have a 1-1/16" Forstner bit..........so I ordered one.........and it should be here Monday from Amazon. I marked the holes so they are ready to go when I get the bit.
To remove the 3/16" stock from the RH and LH sides was relatively easy. I used the old Sears miter saw and it takes a lot of strokes, but I removed the material.
But how to remove the material on the front and back pieces was a challenge, because you have to leave a 5/16" strip on both sides. I decided to use a large, maybe 1.5" diameter round bottom/flat bit on the router table. You have to make stop marks so you don't feed the board too far, and you have to feed it the right way. I kind of expected to make at least 1 mistake, and I made 2............but they are on the inside where nobody will see them. I may fill them with scrap pine, then belt sand flush.
This part of the build went ok, just time consuming.
When I got the top divider and release assembly built, the left hand of the divider did not look quite right. It had a larger gap between the divider and the LH angled shim than the other side.
It seems like the whole divider block should be about 10% bigger. On the LH side, I glued a 3/16" thick pine shim to the oak divider, and now it seems to work ok.
As I was playing around with the mechanism some more, every so often the marble would hang up on the LH side. This mechanism needs to be perfect so the the marbles always come out, and go to the right side.
I went back into Sketchup and reviewed the original design. The 90-year old engineer that built the model probably never heard of the performance sensitivity of a design to the specific design. The original design is very sensitive to the height of the divider in the mechanism, and I may have moved it down a hair because I did not want to drill the 1/8" pivot hole too close to the edge of the material. I increased the size of the design, built another divider from oak........and now it works perfectly !!!!!!
Building this was more challenging than I thought!!
I ended up temporarily gluing 4 glue blocks to the top, 3/4x3/4x 1.5".............so I could screw and then unscrew the 4 sides from each other...........to attach the track.
I used hot melt glue gun to hold the marble track.............which worked great because when I made a mistake, I could easily remove the glued on track..........reposition it.......then glue it again.
Boy it is slow going adding 1 piece at a time to the marble storage unit. I wonder if it would have been faster to lay all 4 sides flat next to each other, then mark 2.5 degree slope across all 4 pieces, to give a line to fit to as you add the track pieces?
I started installing the marble track inside the top box...............at the bottom and worked my way upwards. But when I got near the top, I was too high with respect to the hole you start the marbles at !!!!
I checked the plans and they said the track bottom should be 1/4" thick, and my track bottom is 1/4", so that is not it. I am not sure what is next?
I laid this out in sketchup and it should work..........but I did not account for the thickness of the little angled shims.
Maybe I start at the top and work my way down?
Boy, I wish he would have added 1 inch of height to the main box..........to give plenty of tolerance for installing all the track !
I laid the 4 sides of the box flat, then laid in the lines representing the marble track and marbles. I even thinned up the track bottom from 1/4" the plans say to 3/16".
I also allowed 1/8" thickness for the angled wedges at the corners of the track..........and an 1/8" drop from track to track.
The results of my layout is the track ends up being above the entry hole, not below !! This means it is impossible to make the original design work......using the assumptions noted above. If you eliminate the 1/8" drop from track to track, you might just make it. I like the fact the machine is supposed to run by itself for 6 minutes using 26 marbles.
So, what are my options now?
1. Redo the whole storage box.
Lay out the track lines using printouts from sketchup.
Reduce track to track drop from 1/8" to 0 to 1/16.
Thin up bottom of track from 1/4 to 3/16".
If I do this option, there is still almost no margin for error..............
I was a little surprised to learn the marble storage unit will not work as designed in the plans.
I went into Sketchup to fix the design. After several options, I decided to do the following.....
-abandon my idea of having a removable 3/16" thick luan box. Go back to 1/2" thick walls. I will use screws to make it removable.
-increase box height by 1 inch to allow some tolerance installing the track
-increase 2.5 degrees slope to 3.0 degrees
-allow 1/8" drop at each corner
-allow 1/8" thickness for corner wedges
-mark bottom line of track on all 4 walls laid flat, then build to the line
According to Sketchup, this should work fine and give a better 3.0 versus 2.5 degree slope.
I built from the bottom up, so I had extra space at the top when I got there.
I tested the box with 26 marbles and got about a 95% result........with the 5% being marbles that hung up and did not unload with all 26. One was due to a depression in the bottom of the chute in 1 spot.
I really want this box to be perfect, in that all 26 marbles will unload by themselves over 99% of the time.
To optimize the design, I made a spreadsheet which gradually adds the height of the chutes until you achieve the top height below the hole. I set up the spreadsheet so I can change angle and the chute-to-chute drop. I found that 3.5 degrees is about the optimum design [remember, I added 1" height to the storage box]. I decided the 3rd attempt will be a charm..........so I am going to try round #3 and see if I can build the performance.
I ran out of 1x8 boards to make the 4 new sides, so I glued up 2 pieces of standard 1x4 to make the 4 walls for round #3. This is probably better because of less bowing over time with 2 pieces versus 1.
While I was doing Build #2, I went back and looked at Build #1 to see why it failed so miserable. I discovered I had tried to install 1 extra round of chuting in the box !!!!!!!!!!! I wanted so badly to make sure all 26 marbles would fit which gives the desired 6 minute run time............that I accidentally tried to add an extra round of chuting!! Boy, a picture in the 34 page of plans would have really helped me understand how many rounds of chuting are needed !!!!!!!
I need to update my Sketchup design model, because it has too many layers of chutes in it!!
Gluing up some 1x4's to make the 4 side walls, and quick drying in oven at 120F......
I almost messed up, because I forgot to add the 1/2" on the bottom of each side, because I changed the design. I caught it when I was doing the flat panel pencil layout. I fixed it then printed it out to pencil out where the tracks went on Unit #3.
Boy, I wish I would have had this photo in the 34 pages of plans in the booklet, because a picture is worth a 1,000 words in this case !!!!!!!!
Twice I loaded up all 26 marbles and then by finger actuated the plunger, everything worked flawlessly !! No marbles hung up either. I skipped the little wedges at the corners, they caused me problems on Units 1 and 2 with marbles hanging up. You can use this link to watch a video of the #3 marble unit working great !
I added some lead in a 1/2" hole I bored in the weight board. I also added a wood washer to limit the travel of the plunger pushing up in the marble storage container. After some fiddling, I got it to work consistently. You can watch a video of it working using this link.
Remember not to attach any track to the top marble storage container, so it is removable.
I designed my version to use screws to keep the 4 long vertical sides fastened, and they can be taken apart........as long as you don't attach track to more than 1 vertical piece.
Biggest dowel I have to 1.25" and plans call for 1-3/8". I made round one end of a 6 inch piece of 2x4, cut to 1.5x1.5 inches, so I could chuck it in the lathe.
I got 1-3/8" OD, with a flat I will hide on the back side. I drilled and then inserted a 1" dowel in the bottom.
When I first tried it, the top would only travel about 45 degrees, instead of the 90 degrees needed to dump the ball. I lightened up the lower 1" dowel by drilling a 3/8" center.........and Presto...............it started working like a charm !!
When I got to the section to put in the stair step section, I had run out of room for that much vertical fall. I finally gave up and just put in a regular chute instead of the stair steps......otherwise things went pretty good.
I made 4 steps and the base for the spiral staircase.................from which I could figure out how far to the right I could run the other marble track to finish it.
Had to do some adjustments, like add little squares at end of the track where marble jumped off, etc. Biggest problem was marbles not coming back up after they went down the curve by the handle. I had to think about it for a while, but you want the marble to fall against the left side of the curved track, not straight down.......because you lose the momentum on the marble because it is not following all the track curvature.
I also made the curved piece of track a little long on the RH side, so I could cut it off at assembly to what I needed. I did not realize the left side of the track needs to be 1-1/16" to the left side of the handle, no more !!! Once I figured out how it worked (the marble must follow the curve as it falls)............it now works great.
If it is supposed to take 6 minutes to process 26 marbles, this works out to 14 seconds per marble. I rough timed the RH track and it came in at 13 or 14 seconds!!
The plans call for 1/4" thick steps and 1/8" thick ends. and the 1/4" center dowel is supposed to be 1.5" out from the face. I had to shorten up some steps that go next to the main vertical piece..........but if you make it too short, there is not enough clearance for the marble !!
If I had to do it over again, I would have increase the bottom base to 3.5 inch diameter, giving a 1-3/4" distance of the dowel from the face.
Last thing to do was to get the auto trigger linkage working so that when 1 marble finishes, it automatically triggers the next one. The first issue was that the plunger for the marble storage container was not always falling down with no marbles. I made a new plunger, lubricated everything with Johnson's Wax, and made about 1.5 inch oak washer that hangs at the bottom of the plunger. I also fuzzed some off the lever because it was catching on the divider end. So that got the marble box working ok. I suspect I have some more fine adjustments to make on it, because once in a while a marble hangs up. Work on that later.
I could not get the weights right, so I removed my lead filled top counterweight and replaced it with an oak one.
What really fixed it was changing the design. I had a collar ring at top of the long dowel, which means the bottom bucket had to work against the counterweight. I removed the collar ring........and PRESTO.........she starting working fine !!!!!!!!!!
Game jams up when tray starts to get full, may need to sand the base to direct marbles away from hole? I thought I saw something in the 30+ pages of plans, but can't find it, will have to look again.
Read manual 3 times, nothing about this. I ended taking a 3.5x3.5 inch piece of pine, 1/4" thick and sanding slopes to direct the marbles to the sides of the storage area. I also added an angled block about 3/8" high with a 15 degree slope to drive them away from the exit hole. I need to add this to my drawing.
I used the table saw set to a 15 degree angle and ran the lid through vertically to shape the edges, came out nice!! The knob I used was one I had in my inventory.
I am not sure why, but I can watch the marble machine operate in fascination, then want to reload it to watch it some more !!
Once in a while the marble storage unit malfunctions, which I suspect is caused by......
1. Some marble(s) get hung up in the track and do not descend
2. Geometry not perfect at the loading point, 2 marbles get released at once.....maybe stroke needs reduced a hair?
Guess I need an elongated hole like the plans call for instead of my U-shaped piece.
When I re-read the instruction booklet 3 times looking for a solution to marbles blocking each other in exit tray, I noticed and illustration showing to shim the distance besides the handle to 1-1/16" to the right of the curved drop chute. Since I was still having a few marbles not make it through the curve, I added this shim.
1. set stroke to minimum for plunger storage box plunger
2. Put lead back on Start Button counterweight
3. Had to add about 3/16" to length of long 1/4" dowel. Boy, there is no room for error with respect to the plunger storage box lift and the length of the long 1/4" dowel !!
I usually like to design stuff so it is less sensitive, but I don't see how to do this right now.
4. Ran about 10 cycles of all 26 marbles. Got errors down to 0 on the exterior track. Once or twice I had to push the Start button again, and shake the top box, because a marble was hung up. Otherwise she ran pretty well.
In Sketchup, I increased the diameter of the start button to 2 inches, so I could carbon trace small letters to paint. I used a Plump font in Sketchup. I carbon traced it, then tried to hand paint using pointed artist's brush.........and I failed miserably !! I finally went to a black magic marker with a medium point, and that gave me the best lettering !! I put clear gloss polyurethane on last, to make the black magic marker pop, which is has done on other projects where I faked ebony by coloring oak black with a magic marker.
I decided to paint the bottom side of the track the same as the base unit color, old Fairbury City Hall yellow. On the tracks, I used 2 different colors, light green and light yellow.....and painted outside of track, inside, and ends. I used a 1/2" chip brush and an artist's brush............with the artist's brush for the top of the track next to the square base.
As expected, the addition of paint caused some spots where I had to do a little sanding. I then started running 26 marbles at a time, and fixing any issues that arose.
I was still getting some marbles hanging up in the storage box, so I decided to add the Booster ramps at each corner like the plans call for. On some of those I had to make some adjustments as well.
Eventually, I was able to run the game 10 cycles of 26 marbles each, with no hangups in the storage box, and none fell off the exterior or got stuck !!!!!!!!! I think I have it perfected finally !!!!!!!!
In the big model, the key mechanisms are hidden from the public. I decided to design up a small illustrator version of the model, where people could see how the key mechanisms work.
I have used this thin plastic before on other projects, and I saw it on the scroll saw. But, when I started sawing my first little rectangle for this miniature model, I got some small fractures in the plastic. I had a big blade in the scroll saw, so I switched back to the smallest blade, about a No. 2, and no more problems with fracturing.
I noticed my bottom exit hole was too high, and found I made a design mistake. I was able to fix it by sawing 1/4" off the bottom of the front piece.
Then I did not have a good way to mount the RH side exit chute, so I designed a new wood piece there.
Other than that, everything went together ok.
I was having trouble getting the little game to run in auto mode............finally traced it the vertical dowel rubbing against the inside of the square nut on the bucket lever !! The angle is much steeper on the little vs the large model, so more clearance for the 1/4" diameter dowel is needed. I increased the square nut up to 3/4x3/4x1/2 tall, with a 3/8" hole and it solved the problem :)
WOW, it took a lot of of man-hours to build the 26-marble game. Although there were 33 pages of instructions, they were about as clear as mud. Several 3D views of the key elements of the design would have been priceless in terms of helping to understand how to build it.
2 of my Grandkids have already played with the large model, and they just had a ball with it. My other grandkids, and kids/adults at my public exhibitions should enjoy it as well. There is something mesmorizing about watching the large marble machine run.
The marble game has now gone through a couple of rounds of intensive play by the grandkids, ages 3 to 5. After a couple of hours of very heavy use, including hitting the start button a many times during 1 cycle, it quit automatically releasing the next marble.
Took it back to the shop, and found out when I built it, I had to hot melt glue a 3/16" long piece of 1/4" dowel on the bottom end to get it to work right. Well, the hot melt glue failed from the pounding, and we had shaken the unit to get some marbles out of the interior, and it had popped out of the square holder at the bottom. I plan on making a dowel the right length so there is no hot melt glue joint. I think I was out of 1/4" dowels when I was building it.
Also the start button can hang up on the single spacer to keep it from turning. I think I will get rid of that single spacer also.
Not too bad for a game with many moving parts that all have to work just right !
I tried cheap Birch dowels for the new 1/4" dowel, but they were too bent.........so I went with a piece of straight red oak. I measured the old piece with the little extension piece......and cut a new one. The new one did not work!! I tried a nut next to the bucket, that did not work either. I finally shaved maybe 1/16" from the new dowel, and bingo, it started working!
Boy, this is a sensitive design!! I wish I knew how to de-sensitize it, but I don't.
I ended up screwing around for more than 2 hours trying to get the auto part working flawlessly again. I tried to make a free-body diagram and see how to desensitize the design, but it was not obvious.
I did a little experiment where I only had 1 marble in the top hopper, then sent a marble into the green track. It worked 100% with 1 marble only, makes me wonder if the next marble waiting in line is putting a lot of force on the marble we are trying to lift up over the 2 dowel pins?
The yellow track works fine, but the green sometimes the bucket does not come clear down to release the marble out the exit hole, and release a top storage marble. Only difference I see is that on the yellow side, the marble does drop down maybe a 1/4" giving some velocity when it hits the bucket. There is no drop down on the green side, the hole in the side is too low to allow some drop height. I could change this, but it would be a pain in the rear end to do it.
On my excel spreadsheet, I changed the inputs so 100% of the weight of the waiting ball is transferred to the ball we are trying to lift, and ratio gets very close to 1.0...........which is what I have on my model !!
I studied the storage box function, and the little pivot lever has to raise not only the 1st marble to release it over the dowels, but it has to lift the 2nd marble partially also!!!!!!!!! I tried making a new lever, but that did not work. It will take more time to try to re-optimize this lever so only 1 ball is raised. Boy, if I knew how sensitive this model was, I would have paid more attention to the loading geometry when I built the big unit !!
I don't have problems on the illustrator small model, but the geometry is slightly different in the loading area I think, so maybe less weight is transferred?
Basically to lift the marble in the storage box and release it, you have the weight of the marble going into the bucket times the ratio of the bucket lever..............which works out to about 1.30.........so have 1.30 times the weight of the marble to release it.
When I push up with my finger on either the long dowel, or the plunger below the box, you can feel a transition of force.........starting out very low, then shifting to a little higher resistance. Detaching the storage box and pushing up on the plunger, I could see where the light initial force is just raising the ball to release it..........then you start to push the waiting marble back up its ramp a little until the 1st marble releases.
My system seems pretty robust right now. I could try raising the ramp holding the marble in waiting, but you run the risk of the waiting marble blowing by the 2 dowels after the 1st marble is released. I don't want to mess up my current storage box trying to this out. I would be better off making a new lower assembly that fits into my storage box to try it out. Maybe in my spare time :)